Perpendicular write head with tapered main pole

ABSTRACT

Prior art designs of single pole writers have been limited by premature saturation at the tip. This limits the head field that can be achieved without simultaneously widening the write profile. This problem has bee solved by means of a vertical main pole whose thickness has its conventional value a short distance from the tip but that tapers down to a significantly reduced value as it approaches the tip. A process for manufacturing this tapered tip design is also presented.

This is a divisional application of US patent application Ser. No.10/818,577, filed on Apr. 6, 2004, which is herein incorporated byreference in its entirety, and assigned to a common assignee.

FIELD OF THE INVENTION

The invention relates to the general field of magnetic disk systems withparticular reference to perpendicular write poles and controlling fluxtherefrom.

BACKGROUND OF THE INVENTION

One of the key advantages of single-pole (SP) head/media, with amagnetically soft underlayer (SUL) and perpendicular recording system,is the capability of providing a larger write field (than that of a ringhead) to enable writing into the relatively thick media with highanisotropy constant. The latter quality leads one to assume betterthermal stability associated with perpendicular recording. However, thisadvantage is diminished as the dimension of the pole tip is reduced toincrease the areal recording density [1]. So, the tradeoff between headwriting field and thermal stability may still limit the achievable arealdensity for perpendicular recording.

FIG. 1 is a schematic representation of a typical single pole verticalrecording system of the prior art. Seen there is single write pole 13whose ABS (air bearing surface) moves parallel, and close to, thesurface of recording medium 16. The latter comprises an upper, highcoercivity, layer (not shown) on a magnetically soft underlayer. Coils12 generate magnetic flux in yoke 14 which passes through main pole 14into tip 13 and then into media 16 (where a bit is written). Themagnetic circuit is completed by flux that passes through the soft underlayer and then back into return pole 15. The space enclosed by the yokeand poles is normally filled with insulating material 17.

FIG. 2 is a front view of the structure shown in FIG. 1 when viewedalong direction 18.

An enlarged view of the write and return poles is shown in FIG. 3. Inthis prior art design, the main pole 13 is about 0.1 to 0.4 micronsthick at the ABS 19. The main pole is made of a high moment material,such as CoFe having a saturation magnetization, Bs, of about 2.4 T, but,in practice, this main pole does not saturate, except at the pole tipregion. Thus the maximum write field in the media is mainly determinedby the saturation level of the pole tip and the solid angle opened bythe ABS of the pole tip.

To increase the write field, large W and t and small NH are preferred(as defined in FIGS. 1 and 2). However, for ultra-high densityrecording, track width W is limited by the

track density requirement. To have good control of track width W, NHcannot be reduced to the extent desired due to the rounding effect ofthe photo mask used to pattern it. A small neck height also increasesthe side-fringing field and causes adjacent track erasure (ATE) [2].

A large pole width t will result in head skew problems [3]. Thus bettermethods for compensating field loss at ultra-high recording densitiesare essential. The present invention discloses a novel structure for aperpendicular write head that overcomes these problems.

References:

(1) Z. Bai, and J.-G. Zhu, “Micromagnetics of Perpendicular Write Headswith Small Pole-Tip Dimensions”, J. Appl. Phys, vol. 91, 6833 (2001).(2) J. Schare, L. Guan, J. G. Zhu, and M. Kryder, “Design Considerationsfor Single-Pole Type Write Heads”, IEEE Tran. Magn., May, 2003(3) R. Wood, T. Sonobe, Z. Jin, and B. Wilson, “Perpendicular recording:the promise and the problems”, J. Magn. Magn. Mater., vol 235, 1 (2001)

A routine search of the prior art was performed with the followingreferences of interest being found:

U.S. Pat. No. 5,600,519 (Heim et al) discloses a tapered main pole asdoes U.S. Pat. No. 5,173,821 (Maloney).

SUMMARY OF THE INVENTION

It has been an object of at least one embodiment of the presentinvention to provide a single pole vertical write head having both alarge head field, as well as good spatial resolution.

Another object of at least one embodiment of the present invention hasbeen to provide a process for manufacturing said vertical writer.

A further object of at least one embodiment of the present invention hasbeen that said process introduce little or no changes to currentprocesses for manufacturing vertical writers.

These objects have been achieved by means of a vertical main pole whosethickness has its conventional value a short distance from the tip butthat tapers down to a significantly reduced value as it approaches thetip. Typically, the distance over which this tapering takes place isabout 0.1 to 4 microns. In order to manufacture this structure, a trenchis etched, using ion milling, partly into the yoke region and partlyinto the insulated coil well. Said trench has sides whose slope iscarefully controlled through adjustment of the angle of incidence of theion beam, this slope determining the aforementioned taper. After thetrench has been just filled with a high moment layer, a second highmoment layer is deposited to complete formation of the pole tip. Afteran appropriate lapping step to define the ABS, the process is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a single vertical pole magnetic writer of the prior art.

FIG. 2 is a head-on view of the structure of FIG. 1.

FIG. 3 is a closer view of the pole tip portion of a vertical writer

FIG. 4 shows the starting point for the process of the presentinvention.

FIGS. 5 and 6 illustrate formation and filling of a trench with a highmoment material.

FIG. 7 shows deposition of a second layer of high moment material overthe afore-mentioned first layer.

FIG. 8 shows the final structure.

FIG. 9 compares the magnitude and spatial distribution of the head fieldin a device made according to the present invention with two prior artdevices.

FIG. 10 is a cross-section of the write head, including an ABS levelshield.

FIG. 11 is an ABS view of FIG. 10 for a single trailing edge shield.

FIG. 12 is said ABS view for a shield that surrounds the main pole onthree sides.

FIG. 13 is an example of a tapered main pole at a trailing edge combinedwith a trailing shield

FIGS. 14-20 illustrate the process for making the structure shown inFIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

We will disclose the present invention through a description of aprocess for its manufacture. This description will also serve to makeclear the structure of the present invention.

Referring now to FIG. 4, the process of the present invention beginswith the formation of return pole layer 15 on a substrate (not shown).Layer 15 is any of Ni, Fe, or Co, or their alloys and it is deposited toa thickness between about 0.5 and 5 microns. This is followed by theformation of magnetic yoke 14 that includes a well within which is coil12 embedded in layer of insulation 17. Yoke 14 is a material such as Ni,Fe, Co, or their alloys.

Now follows a key novel feature, namely the formation of trench 51, asshown in FIG. 5. Ion beam milling is most commonly used to form saidtrench whose depth is typically between about 0.1 and 2 microns , thisdepth being controlled through adjustment of the ion beam's dose andduration. Walls 52 of trench 51 have sloping sides as shown in thefigure. The sides of the trench slope at an angle between about 15 and65 degrees from vertical, slope angle being controlled throughadjustment of the ion beam's angle of incidence.

Trench 52 is then overfilled with layer 61 of a material capable of amagnetic moment of at least 1.8 T and is then planarized untilinsulation layer 17 is just exposed, as illustrated in FIG. 6. Layer 61should have high Bs and is any of Ni, Fe, or Co, or their alloys.

Next, as seen in FIG. 7, layer 71 of a material capable of a magneticmoment of at least 2 T, is deposited. Layer 71 is any of Ni, Fe, or Co,or their alloys. This essentially completes formation of the magneticwrite head which, as can be seen, now includes a tapered single verticalpole. All that remains to be done is to form air bearing surface 19through planarizing in a plane normal to the upper surface of layer 71.The final structure is seen in FIG. 8.

FIG. 9 compares calculated plots of the head field (in Tesla) as afunction its downtrack position (in microns) for three cases: Curve 91is a conventional straight pole design having t=0.2 microns. Curve 92 isa straight main pole having t=0.4 microns, while curve 93 is for atapered main pole (present invention) (t1=t2=0.2 microns, and NH=0).These data make it clear that the head field can be increased byproviding a thicker main pole (curve 92) but this comes with anaccompanying problem that the head field could erase data on adjacenttracks when the head is skewed. On the other hand, a main pole designedaccording to the teachings of the present invention (curve 93) achievesa head field even larger than that of the thicker, but conventional,pole with less erasure problems for the same head skew angle because ofsmaller pole thickness at the ABS.

The concept of a tapered main pole is not limited to only single poleperpendicular writers, but is also applicable to a shielded pole typeperpendicular write head, a cross-section of which is shown in FIG. 10with the shield being designated as element 25. Shield designs may vary.For example, in FIG. 11 we show an ABS view of shield 26 which islocated on only one side (the trailing edge), while in FIG. 12 we showshield 27 that surrounds the main pole on three sides (trailing edge andtwo sides in the cross-track).

In addition to the previously described tapered main pole structure at aleading edge, a tapered main pole at a trailing edge, combined withtrailing shield 135, is disclosed here, as shown in FIG. 13. Note thatthe trailing shield is tapered to the same angle as the main pole,thereby maintaining a constant horizontal distance 131 therefrom.

The major process steps to make this trailing-edge-tapered main polewith trailing shield are illustrated in FIGS. 14-20. FIG. 14 shows thestarting point for manufacturing the writer once the reader structurehas been completed. First, isolation 41 layer (usually Al₂O₃, betweenabout 1 and 3 um thick) is deposited on the top reader shield 42,followed by layer 43 of high Bs materials (Co, Fe and their alloys,Bs˜2.4 T, thickness about 0.2 to 2 um), which will eventually form themain pole. In FIG. 15, an etching process similar to that shown in FIG.5, is applied to form trench 151, whose slope angle defines the taperangle of the main pole. Subsequently, the process to define main poletrack width is applied so the front geometry of the main pole (as inFIG. 2) is formed. In FIG. 16 non-magnetic layer 141 (usually Al₂O₃,0.03 to 0.2 um thick) is deposited to serve as the gap between thetrailing shield and main pole. In FIG. 17, trailing shield 135 (alloysof Co, Fe, Ni, Bs around 1.0-2.0 T) is deposited on top of gap layer141. In FIG. 18, coils 12 are made. Then the whole structure is filledwith Al₂O₃ and polished to expose the top surface of the trailingshield. In FIG. 19, the return pole (alloys of Co, Fe, Ni, Bs around1.0-2.0 T, thickness=0.5-5.0 um) is deposited and connected with thetrailing shield. Finally, in FIG. 20, lapping is applied to define theABS of the head.

What is claimed is:

1. A magnetic write head, having an ABS, a main pole, and a trailingedge, comprising: said trailing edge being tapered at an angle of 15 to60 degrees from vertical; wherein said taper of the trailing edge beginsat a distance of less than about 0.3 microns from said ABS; wherein saidtaper of the trailing edge is present over a distance of up to about 2microns from said ABS; behind said main pole, a trailing shield having athickness between about 0.05 and 0.5 microns; wherein there is aconstant horizontal separation between said main pole and said trailingshield; and wherein said shield is tapered at an angle equal to saidmain pole taper angle.
 2. The magnetic write head described in claim 1wherein said constant separation between said main pole and saidtrailing shield is between about 0.02 and 0.2 microns.
 3. The magneticwrite head described in claim 1 further comprising one or more sideshields around said main pole.
 4. The magnetic write head described inclaim 4 further comprising: a return pole; on said return pole, amagnetic yoke that includes a well within which is a coil embedded in alayer of insulation having a first upper surface; a trench, having afloor and a sloping sidewall, formed from said first upper surface; afirst layer of a material, capable of a magnetic moment of at least 1.8T, that more than fills said trench and that has a second upper surface;and on said second upper surface, a layer of a second material capableof a magnetic moment of at least 2 T.